Micro Injector/Capillary Method

The micro-injector works by attaching the valve of a cylinder to a micrometer such that with great precision the valve can be pushed into the cylinder to create a pushing force or it can be drawn out to create a sucking force.  Figure 1 is a CAD that shows how this method would be implemented.

Figure 1. XenoWorks Analog Micro-Injector

Figure 2. 2D CAD of Vacuum Method

Figure 3. Sutter Micro injector

Table 1. Pros and Cons of Vacuum Method

Current Testing Status:

It was found that the sample micro injector tips that arrived from Sutter could also be used as capillary tubes.  While we waited for our micro injector to arrive we decided to test the capillary method first by using the tips from Sutter with no holder attached to it.  

Sample tips were found to indeed remove water but it was difficult to verify whether the tip has removed water from the well.  It was discovered that the glass tips must be handled with care or else they will break as shown in Figure 6 which is taken while testing the tubes on an unstable XY-stage design shown in Figure 5. Vibration was critical in this setup. Ambient vibrations could break the tip. Because our sponsor does his research in a bio-hazard level 3 facility, there are very strict rules about broken materials especially sharp materials such as glass. Working around HIV it can be very dangerous to have sharp materials.  If a scratch from the broken glass draws blood the researcher is at risk of getting HIV. Therefore, a stable design was implemented to account for these requirements as shown in Figure 4. A pneumatic table was used to draw out vibrations. Also the PDMS material used on the slides gave the glass more cushion in case it was forced on the slide. 28 tests were carried out with different parameters such as trajectory (touching or not touching the slide) and the number of revolutions of the fine dial shown in Figure 3. There were no broken glass tips while testing. Out of the 28 tests, 70% tests were successful. Optimal parameters were chosen in which 5 consecutive tests were 100% successful in picking up the bead.

Figure 4. Stable Design for Vacuum Method (Week 10)

Video showing successful bead pickup using apparatus in Figure 4

Figure 5. Unstable Apparatus for Vacuum Method (Week 1)

Figure 6. Example of a capillary tip hitting micro-array, buckling, and shattering

Using Apparatus in Figure 5

Video Showing the Results from Using Apparatus in Figure 5